JNTU B.Tech II ELECTRICAL ENGINEERING Previous Question Paper (May/June - 2019 - R13)

Define self and mutual inductance.

State Ohm’s law. What are the limitations?

What is the importance of RMS value?

Give any three merits of three phase system.

How may the direction of rotation of DC shunt motor be reversed?

Based on type of excitation classify the DC generators.

Define efficiency and regulation of a transformer.

Explain the principle of operation of a three phase induction motor.

Explain the working of an alternator.

What is meant by synchronous impedance method?

State and explain Faraday’s laws of electromagnetic induction.

A coil of 1000 turns of wire uniformly wound on a non-magnetic ring of mean diameter 40 cm and cross-sectional area of 20 sq. cm. Calculate:

1. The inductance of the coil.
2. The energy stored in the magnetic field, when the coil is carrying a current of 15 A.
3. The emf induced in the coil, if this current is completely interrupted in 0.01 second.

Explain the principle of permanent magnet moving coil meter.

If Ra, Rb, and Rc are connected in star, derive the expression for equivalent delta connection.

Derive the expression for root mean square value of an alternating sinusoidal current wave form I = Im Sinθ.

A reactor having negligible resistance and an inductance of 0.1 H is connected in series with a resistor of 15 ohms. The circuit is connected across a 230 V, 50 Hz, single phase AC supply, Find:

1. Current flowing through the circuit.
2. Power factor of the circuit.
3. Voltage across the reactor.

Derive the expression for average value of an alternating sinusoidal current wave form I = Im Sinθ.

A capacitor of 100 µF is connected across 200 V, 50 Hz, single phase supply:

1. The reactance of the capacitor.
2. RMS value of the current.
3. The maximum value of the current.

Explain the principle of operation of d.c generator.

A 4 pole DC generator with a shunt field resistance of 100 Ω and armature resistance of 1 Ω has 378 wave connected conductors in its armature. The flux per pole is 0.02 Wb. If a load resistance of 10 Ω is connected across the armature terminals and the generator is driven at 1000 rpm, calculate the power absorbed by the load.

What are the differences between a DC shunt motor and a DC series motor.

A short shunt D.C compound generator supplied 7.5 KW at 230 V. The shunt field, series field, and armature resistances are 100 Ω, 0.3 Ω, and 0.4 Ω respectively. Calculate the induced emf and the load resistance.

Explain the principle of operation of a transformer. Draw the phasor diagram for the transformer on no load.

A single phase transformer working at unity power factor has an efficiency of 90 % at both one half load and at the full load. Determine the efficiency at 75 % of full load.

Explain with the help of diagrams how a rotating magnetic field is produced in a 3 phase induction motor.

A 3-phase, 6 pole, 50 Hz induction motor develops 4 kW including friction and windage losses at 950 rpm. If the stator loss is 250 W, find the rotor frequency.

Explain conduction of o.c test on alternator.

A 3-phase, 6 pole star connected alternator revolves at 1000 rpm. The stator has 90 slots and 8 conductors per slot. The flux per pole is 0.05 wb. (Sinusoidally distributed). Calculate the voltage generated by the machine, if the winding factor is 0.96.